Reversibly rendering non-explosive nitric acid esters



United States Patent C) 3,140,211 REVERSIBLY RENDERING NON-EXPLOSWE NITRIC ACID ESTERS I Adolf Berthmann and Clemens Franze, both of Leverkusen, Germany, assiguors to Dynamit Nobel Aktiengesellschaft, Troisdorf, Bezirk Cologne, Germany, a German corporation N Drawing. Filed Apr. 24, 1962, Ser. No. 189,716 Claims priority, application Germany Apr. 25, 1961 18 Claims. (Cl. 149-101) This invention relates to the reversibly rendering nonexplosive of explosive nitric acid esters.

It is extremely hazardous to store and transport explosive liquid nitric acid esters, such as nitroglycerin due to the high sensitivity of these materials to be detonated by percussion, etc.

Various proposals have been made to temporarily render these materials non-explosive or less sensitive to explosion by percussion detonation in order to allow the transport and/or storage thereof.

In accordance with United States Patent 2,694,404, it has been proposed to transport nitroglycerin through pipe lines by forming an aqueous emulsion thereof in water by injection. While the emulsion is safe from danger of explosion, it tends to physically separate into its phases so that the process is mainly suitable for the transportation of the nitroglycerin through pipe lines, and it is not suitable for storage, transportation in containers, or the like.

It has also been proposed to desensitize nitroglycerin with respect to its tendency to' explode by dilution with organic liquids and thus to render the same safe for transportation, storage, etc. In accordance with one proposal, ethyl acetate is used as the desensitizer. The flash point of the ethyl acetate-nitroglycerin mixture is, hoW- ever, very low, creating a new danger from the storage and/ or handling and furthermore, it is only possible to use the ethyl acetate if the nitroglycerin is intended for very specific purposes, as for example, the production of powder.

Methanol, dioxane, and acetone have also been proposed as the organic liquids for the dilution of the nitroglycerin. These materials also have a high vapor pressure and consequently a low flash point creating the danger of a possible space explosion. Additionally, these organic liquids are not readily separable from the nitroglycerin by a simple extraction with water. Thus, for example, mixtures of equal parts by volume of the nitroglycerin with these organic liquids followed by a single stage extraction with a like quantity of Water will, in the case of methanol, leave about a residue in the nitroglycerin. In the case of acetone, about a 55% residue, and in the case of dioxane, about a 50% residue.

Thus, complete removal of these organic liquids requires a multi-stage extraction which involves a considerable technical expenditure.

One object of this invention is the reversibly rendering non-explosive of an explosive nitric acid ester, e.g., nitroglycerin, nitroglycol, diglycolnitrate etc., without the above-mentioned disadvantages. A further object of this invention is the rendering non-explosive of an explosive nitric acid ester, e.g., nitroglycerin in such a manner as to allow its recouversion to an explosive form in a very simple and economic manner.

3,146,211 Patented July 7, 1964 ice These and still further objects will become apparent from the following description:

In accordance with the invention, it has been found that explosive nitric acidesters, e.g.,.nitroglycerin, may be eifectively and easily rendered. non explosive by admixture at normal temperature With. a polyglycol; e.g'., a dior triglycol, or polyglycols with a molecular weight up to 5000-6000. It has furthermore been found that the explosive ester, such as the nitroglycerin, .nitroglycol, diglycolnitrate etc., may be again recovered in an explosive form fromthe mixture in a simple and economical manner by a single stage extraction with water.

In accordance with the invention, the explosive ester, such as the nitroglycerin, is simply admixed at normal temperature in any conventional manner with 20 to 60 and preferably 45 to 55% by weight of the polyglycol.

The 2.0% by weight of polyglycol constitutes the minimum amount for truly safe handling andwith this amount the mixture in a drop-hammer, test according to Kast (Posts Chemisch-technische Analyse, 3rd ed. (1909), vol. II, No. 3) will not be detonated by the fall of a 5 kilogram hammer from a height of 40 centimeters. In contrast thereto, if the mixture only contains 15% by weight of polyglycol, the same will be detonated with a 2 kilogram weight falling from a heightof 6 0 centimeters.

While larger amounts than 60% of the polyglycol may be used, such larger quantities are not desirable for economic reasons.

Mixtures containing the preferred amount of polyglycol of 45-55% may be considered completely nonexplosive and will not detonate even when using a number 8 detonating cap or under the drop hammer.

The polyglycols are substantially completely miscible with the esters, such as the nitroglycerin, nitroglycol diglycolnitrate etc., and with water, and may be substantially completely separated from the ester by a singlestage extraction with water. The amount of water added depends on the amount of polyglycol in the ester-polyglycol mixture. It has been found, that 40-80% by weight of water, and preferably within the range of 5060% relating to the aqueous phase is sufficient for a good extraction. The extraction may be effected by merely adding and mixing Water with the ester-polyglycol mixture and allowing phase separation wherein the ester, such as the nitroglycerin separates as :a lower phase, and the water containing polyglycol as the upper phase. The extraction may be conducted at a temperature in the range of 0-60 C., and preferably in the range of 1030 C.

The mixture of the explosive ester, such as the nitroglycerin with the polyglycol, in addition to being nonexplosive, and therefore safe in this respect for storage and transportation is physically stable, i.e., no separation tends to occur so that the same may be stored in large quantities for long periods of time and the explosive ester, such as the nitroglycerin may be readily recovered in explosive form as needed by simple mixture with water. The mixture is furthermore completely suitable for continuous transportation through pipe lines or for batch transportation in containers.

Furthermore, the ester polyglycol mixture has a relatively high flash point as for example of about degrees C. so that there is practically no danger of ignition in the gas phase.

While the separation of the ester, such as a nitroglycerin from the water-polyglycol phase upon the aqueous extraction proceeds relatively quickly, a certain quantity of the aqueous solution remains emulsified in the nitroglycerin for a longer period of time and may, according to the dimensions of the separator, require, for example, 24 hours for separation, and thus to obtain a completely clear nitroglycerin.

In accordance with an embodiment of the invention it has been found. that nitroglycerin containing such emulsified aqueous solution may be .very quickly cleared by addingafew'percent, as for example 1-3%, of a polyglycol which causes the formation of a completely homogeneous mixture. Smaller or larger additions of polyglycols are operable and mixtures .of polyglyco s can be used. J

'Furthermore, it .has been found that the nitroglycerinwhich contains this minor amount of the polyglycolis substantiallymore thermally stable than une treated nitroglycerin without expense. of its explosive characteristics.

{'With the use of the invention, it is thus possible to desensitize a specific quantity of nitroglycerin, as for example,'by addition of equal parts by weight of a die, trior polyglycol of for example, a molecular weight of 2.00 resulting in the formation of a completely safe mixture which may be transported in cans or similar containers. At the pl'a'ceof use, the nitroglycerin may be recovered in active explosive form by adding similar quantities of waterand separating the nitroglycerin as the lower phase which forms 'which is-supplied to the user.

' The aqueous polyglycol solution obtained after the separation may be treated for the recovery of polyglycol in the conventional manner, as for example, by distil-v lation, extraction, etc. 7

The following examples are given by way of illustration and not limitation:

Exa le 1 part n glyceri mix d th P s glycolf, mixture no longer showed any bulging in the lea block cs r i' g to T auz ('Be op spr st tt n Ziindm tt l 1 1 Ed. (1 3 pand. ou d n be deto ted u e the o am t st a eight at fall of 40 m- A ter d i n of pa ts f wa r t abou twov layer are f d, whe ei the we is practica ly pur n r yc rin. and th up er: Pha ons t Qt a 59% queous triglywl solution. l i

. Example 2 To the again sensitized nitroglycerin obtained accord-. ing to Example 1, which was still turbid, 1 weight percent triglycol was added, whereby a clear solution re: sulted. This nitroglycerin did not differ with respect to data of tcchnics'of explosive, from normal not treated nitroglycerin. However, a considerable increase of its thermalstability was observed. While the untreated nitroglycerin was, according to the Abel test Kast and Metz, Chemische 'Untersuchung der Spr engund Ziindstofie (1944), Braunschweig) stable for about 13 minutes, this value increased through the addition of 1% and triglycol to 2-3 minutes and 40 minutes respectively.

Still more strongly marked was the eflect in the stabilization evaluation accoding to the so-called Hansen test (see also Kast and Metz While with normal nitroglycerin hours a pH value of 3.5 was observed, after. addition of 1% triglycol (or diglycol) after 56 hours a pH value of 6.1 set in, i. e., the nitroglycerin had become extraordinarily stable.

The aqueouspolyglyool solution resulting after the separation, whether through distillation or extraction, etc., may again be worked up to pure polyglycol. Since a nitroglycerin-polyglycol mixture in. the ratio. of 1:1 (on the basis of weight) dissolves about 7% water homogeneously, it is suflicient if for this case the water is removed from the polyglycol only partially.

Example 3 Example 1 was repeated using in place of the nitro glycerin, nitroglycol. A comparable result is obtained.

Example 4 Example 1 was repeated using in place of the nitro glycerin, diglycolnitrate. A comparable rcseult is obtained. i

amp e 5 Example 1 was repeated using in place of the nitroglycerin, a mixture of ,60 parts nitroglycerin and 40 parts nitroglycol. A comparable result is obtained.

Example 6 Examples 1 to 5 were repeated using in each case in place of the triglycol, diglycol, a polyglycol with a molecular weight of about 200, and a polyglycol with a molecular Weight of about 5000-6000 in turn. The ex-- traction in the case of diglycol has been conducted at 10 C., for a polyglycol with a molecular weight of about ;200,a t 30 C., and for a polyglycol with amolecular weight of 5000-6000 at about 50 C. In each case comparable results are obtained.

While the invention has been described in detail with reference to certain specific embodiments, various changes and modifications which fall within the spirit of the invention and scope of the appended claims will become apparent to the skilled artisan. The. invention, therefore, is only intended to be limited by the appended claims 'or their equivalents, wherein we have'endeavored to claim all inherent novelty. We claim:

1. Process for reversibly rendering non-explosive an explosive nitric acid ester which comprises admixing the ester with about 20-60% by weight of a polyglycol to form a solution of the ester and polyglycol.

2. Process according to claim 1 in which the explosive nitric acid ester is admixed with about 45-55% by weight of the polyglycol.

3. Process for temporarily rendering non-explosive an explosive nitric acid ester which comprises admixing the ester with about 20-60% by weight of a polyglycol to form a solution of the ester and polyglycol and there.- after to again activate the ester to explosive form, separating the polyglycol by aqueous extraction.

4. Process according to claim 3 in which the ester is admixed with about 45-55%, by weight of the polyglycol.

5. Process according to claim 4 which includes clarifying the ester obtained after said aqueous extraction by adding thereto polyglycol in an amount sufiicient for clarification without adversely aifecting the explosive char.- acteristics thereof.

6. Process according to claim 5 in which about 13% Y- Weight of poly y l d dr 7. Process for-reversibly rendering non-explosive nitroglycerin which comprises admixing the nitroglycerin with about 20-60% by weight of the polyglycol to form a solution of the ester and polyglycol. i

8. Process, according to claim 7 in which the nitroglycerin is admixed with about 45-55% by weight, of p y ycol- 9. Process according to claim 8'in which said polyglycol is triglycol. 10. Process for temporarily rendering non-explosive nitroglycerin which comprises admixing the nitroglycerin with about 20-60% by weight of the. polyglycol to form a solution of the esterand polyglycol and thereafter to again activate the nitroglycerin to. explosive form, separating the polyglycol by aqueous extraction.

11. Process according to claim 10- in which the nitroglycerin is admixed with about 45-55%, by weight of the polyglycol.

16. A solution of nitroglycerin in about 2060% by weight of a polyglycol.

17. A solution of nitroglycerin in about 45-55% by weight of a polyglycol.

18. A solution according to claim 17 in which said polyglycol is triglycol.

References Cited in the file of this patent UNITED STATES PATENTS Hibbert June 26, 1917 Fassnacht July 10, 1934 

1. PROCESS FOR REVERSIBLY RENDERING NON-EXPLOSIVE AN EXPLOSIVE NITRIC ACID ESTER WHICH COMPRISES ADMIXING THE ESTER WITH ABOUT 20-60% BY WEIGHT OF A POLYGLYCOL TO FORM A SOLUTION OF THE ESTER AND POLYGLYCOL.
 14. A SOLUTION OF AN EXPLOSIVE NITRIC ACID ESTER IN ABOUT 20-60% BY WEIGHT OF A POLYGLYCOL. 